A longstanding dogma, based on lack of efferent synapses, is that odor sensitivity is not modulated at the level of the olfactory receptor neurons (ORNs). The sensation of smell occurs in part by the activation of smell receptors present on the ORNs. This activation begins through contact of the chemical signature responsible for the odor with a smell receptor on the ORN. There is a need to be able to modulate sensitivity to smell, to for example, decrease sensitivity to smell in noxious environments and increase sensitivity to smell for environments in which it is desirable to smell the odors. Disclosed are methods and compositions which modulate the sensitivity to odor responsiveness.